Structure-function study of the extracellular domain of the human IFN-alpha receptor (hIFNAR1) using blocking monoclonal antibodies: the role of domains 1 and 2.
We have performed a structure-function analysis of extracellular domain regions of the human IFN-alpha receptor (hIFNAR1) using mAbs generated by immunizing mice with a soluble hIFNAR1-IgG. Five mAbs described in this study recognize different epitopes as determined by a competitive binding ELISA and by alanine substitution mutant analyses of the hIFNAR1-IgG. Two mAbs, 2E1 and 4A7, are able to block IFN-stimulated gene factor 3 (ISGF3) formation and inhibit the antiviral cytopathic effect induced by several IFN-alpha (IFN-alpha 2/1, -alpha 1, -alpha 2, -alpha 5, and -alpha 8). None of these anti-IFNAR1 mAbs were able to block activity of IFN-beta. mAb 4A7 binds to a domain 1-hIFNAR1-IgG but not to a domain 2-hIFNAR1-IgG, which suggests that its binding region is located in domain 1. The binding of the most potent blocking mAb, 2E1, requires the presence of domain 1 and domain 2. The most critical residue for 2E1 binding is a lysine residue at position 249, which is in domain 2. These findings suggest that both domain 1 and domain 2 are necessary to form a functional receptor and that a region in domain 2 is important. IFN-beta recognizes regions of the hIFNAR complex that are distinct from those important for the IFN-alpha.
Lu
J
J
Department of Antibody and Bioassay Technology, Genentech Inc., South San Francisco, CA 94080, USA.
Chuntharapai
A
A
Beck
J
J
Bass
S
S
Ow
A
A
De Vos
A M
AM
Gibbs
V
V
Kim
K J
KJ
D000409:Alanine / Q000235:genetics; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution / Q000235:genetics; D000818:Animals; D019138:Antibodies, Blocking / Q000378:metabolism / Q000494:pharmacology; D000911:Antibodies, Monoclonal / Q000378:metabolism / Q000494:pharmacology; D001666:Binding Sites, Antibody; D001667:Binding, Competitive / Q000276:immunology; D016860:CD4 Immunoadhesins / Q000276:immunology / Q000378:metabolism / Q000502:physiology; D005110:Extracellular Space / Q000737:chemistry* / Q000276:immunology* / Q000378:metabolism; D006801:Humans; D016898:Interferon-alpha / Q000037:antagonists & inhibitors / Q000276:immunology / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009101:Multiple Myeloma; D016297:Mutagenesis, Site-Directed; D017434:Protein Structure, Tertiary; D053633:Receptor, Interferon alpha-beta; D017471:Receptors, Interferon / Q000737:chemistry* / Q000276:immunology* / Q000378:metabolism; D012995:Solubility; D013329:Structure-Activity Relationship; D014407:Tumor Cells, Cultured
D019138:Antibodies, Blocking; D000911:Antibodies, Monoclonal; D016860:CD4 Immunoadhesins; D016898:Interferon-alpha; D017471:Receptors, Interferon; D053633:Receptor, Interferon alpha-beta; D000409:Alanine